EFFECT OF lODINE DEFICIENCY ON THE REPRODUCTIVE PERFORMANCE OF FEMALE RATS AND THE VIABILITY AND GROWTH RATE OF THEIR PROGENY Vappu Kossila and Ritva Myllymaa Department of Animal Husbandry, University of Helsinki Received January 10, 1970 lodine deficiency and goitrogenic substances in the diet have been reported to decrease the reproductivity ofsheep (Flux et al. 1960) and hen (Rogler 1958, Rogler et al. 1959). Thyroidectomy of pregnant sheep (Falconer 1965) and goats (Ekman 1965) reduced severely the viability of the new-born. In rats, thyroidectomy decreased the ovarian function (Evans et al. 1960). Thyroactive substances, in turn, increase the weight of the ovaries and uterus in mice (Soliman & Reineke 1952), the ovarian responsiveness to equine gonadot- rophin in rats and mice (Johnson & Meites 1950), the response of the uterus to oestradiol in rabbits (Vaes 1960), and the fertility of sheep (Hart 1960, Ryle 1961) and cows (Tur- ner 1959). In larger farm animals iodine deficiency causes reproductive failures primarily through development of a goitrous condition in the fetus (Guilbert 1942). In rat, however, storage of 1131I131 (Gorbman & Evans 1941) and follicular differentiation (Gorbman 1955) of the fetal thyroid begins on the 19th day ofgestation, which is comparatively much later than in some larger species. Once initiated, the differentiation may be speeded up by TSH (Sethre & Wells 1951). The goitrogenic action on the fetus of thiouracil given to mother is seen only after follicular differentiationof the fetal thyroid has occurred (Logothetopoulos & Scott 1956). Thus it is uncertain, whether iodine deficiency or goitrogens in the diet of the mother rat have time to act on the fetal thyroid before thebirth of the pups. In experimental conditions thyroid insufficiency can be induced, among others, by thyroidectomy, by feeding goitrogenic substances like thiouracil, or by feeding an iodine deficient diet to the animals. In thyroidectomized or thiouracil treated rats, however, a high iodine diet or thyroxine analoques possessing no iodine may be thyromimetic (Hsieh 1962, Aslino & Evans 1963, Griesbach et al. 1963, Jorgensen & Wiley 1963). Further- more, thiouracil and a number ofother goitrogens have exhathyroidal effects (Gaunt et al. https://www.c-info.fi/en/info/?token=WKe-4Nww-Aat2tRA.ppJvtx-6-JRubkDlj7p5ug.aWwIDhslIcFK9hUAK4RwQJ3IfiRlczG0nzaN6XXSgNl87UzLiB2Tu_6GDfFUIQWK-8P_zN1dvCXNlbzcGfy6bw4iss-5MY60E2NRXDtGQ2_ivyVof_A4_CK10BEUzxgx0TOBIvjyW3hz1-_Q85enSCctu0lHl4R5IFB_-HaTo69UB5WX7q3zzjCMu4nlAw 1965), and although a goitrous condition can be induced rapidly in animals with goitrogens (Shultze & Turner 1947, p. 33), the resulting physiological condition is apparently not identical with that induced merely by a simple iodine deficiency. lodine deficiency can be easily induced in experimental animals by limiting the iodine intake while simultaneously increasing the calcium content of the diet (Thompson 1933). An excess of calcium may limit, however, in addition to the iodine, also the utilization of other elements essential or beneficial for the reproductional functions (ref. Lamming 1966, p. 9). The present study was designed in order to find out whether the shortage ofiodinealone reduced the reproductive performance of female rats, and the viability, growth rate, and fertility oftheirprogeny when fed with a diet balanced in respect ofother nutrients. Table 1. Composition of the diets used during the experiment. Commercial diet 2 ) Basic components Oats Wheat Barley Wheat germ Soya meal Fish » Whale » Grass » Bone » Brewer’s yeast Milk powder, fat-free » » with fat Corn oil Minerals -(- vitamins Minerals & vitamins per 100kg diet Vitamin A » E » Dj Folic acid Thiamine Riboflavin Niacin Ca-pantothenate Choline NaCl FeSOj MgS04 MnS0 4 CuSO, ZnS0 4 lodine CoS0 4 »/ 'o 22 II 12 5 10 10 6 3 3.6 2.0 7.0 6.0 1.0 0.4 6.5 mill.l.U. 8g 240 000 I.U. 0.05 g 0.20 » 0.40 » 2 » 1 » 10 » 200 » 50 » 30 » 10 » 0.1 » 1.0 » 0.1 » 0.1 » *) KI was excluded from the iodine deficient diet. 2 ) These vitamins were added into the diet at the beginning of Experiment 11. 2) Mankkaa’s Mouse and Rat Diet. S e misynth etic diet Basic components % Casein 30 Glucose 54 Sesam oil 10 Ground cellulose 2 Mineral salt mixture 4 Mineral salt mixture % CaC03 6.860 Ca-citrate 30.830 CaHPOj • 2H20 11.280 K2 HP04 21.880 KCI 12.470 NaCl 7.710 MgS04 sicc. 3.830 MgCOj 3.520 Fe (III) amm. citrate 1.526 MnSG 4 • HaO 0.020 CuSOj • 5H20 0.008 KI l) 0.004 NaF 0.050 AINH4(S0 4) 2 • 12HaO 0.009 Vitamins per 1 kg feed /1-carotene 3.00 mg Calciferol 0.01 » Vit. E. acetate 40.00 » Thiamine HCI 2.00 » Riboflavin 4.00 » Pyridoxine 4.00 » Ca-pantothenate 10.00 » Niacin 0.3 g Inositol 1.0 » Choline 1.0 » p-amino benzoic acid 0.3 » Folic acid 2 ) 0.02 mg Biotin 2 ) 0.0001 mg 138 139 Material and methods Diet. The compositon of the semisynthetic diet (control and iodine deficient) (ref. Rauen 1964) as well as the commercial mouse and rat diet used in this study are given in Table 2. Experiment I. First generation and its progenyfrom the first gestation. Group No. of Pups born No. of Mean at 30 days post partum at 60 days post partum* * dams days after pups birth Survival Mean body No. of Body Thyroid Relative Weight mating born weight weight pups weight weight thyroid of the of the pups weight testes g % g g g . „ , - in „ QO , , Q 0,, / 13(J 178.7 6.0 3.47 1.954 A, Control 10 31.2 82 4.18 31.7 43.5 J. [35 136.0 (see Table 3) « t j c • , An a ok oa k . r o j6(J 183.5 16.4 8.97 2.222 C, I-deficient 10 34.1 49 4.05 24.5 45.3 147 0 ( seeTable 3) * two dams failed to conceive * * (J pups werekilled at 60 days of age $ » weremated at 70 days of age Table 3. Experiment I. Second generation and its progenyfrom the first gestation. Group No. of dams Pups born No. of pups Mean birth at 25 days post partum days after born weight Survival Mean body Thyroid Relative mating weight of the weight thyroid pups weight g % g mg A2Control 13* 27.1 91 4.6 76.9 43.7 4.1 9.14 C2I-deficient 5* 33.8 38 4.8 73.4 46.1 13.8 30.73 * These dams had received from the beginning of their gestation period semisynthetic diet into which folic acid and biotin had been added (Table 1). 140 Table 1. When a sample of the iodine deficient diet was analyzed in the laboratory of the State Agricultural Chemistry, Helsinki, no iodine was found. Seppänen (1969) noted that small amounts of folic acid and biotin were beneficial for the growth of rats, these two vitamins were added into the semipurified diet at the beginning of Experiment 11, although also second generation rats in Experiment I (Table 3) received these vitamins. Blood analyses. Blood was drawn from the heart of anesthetized adult ? rats this treatment leading to the death of the rats. Blood hematocrit(He) values were determined by the microcapillary method with International Centrifuge (14000 RPM 5% minutes). The serum protein bound iodine (PBI) was estimated by the routine clinical method in the Laboratory ofthe State Serum Institute, Helsinki. Organs. The thyroid gland was removed from each experimental animal in the autopsy. The gland was immediately weighed. The relative thyroid weight was calculated in mg/100 g body weight of the rats. The total weight of the female sex organs (uterus -f- -vagina + ovaries -f- tubes) and the weight of the testes were also estimated in most cases. Experimental design. Experiment I was carried out with 20 adult female rats (Tables 2 & 3) and 5 adult males. The experiment was repeated with these and 10 additional females (Experiment II) (Table 4). These 30 females have been considered as a first gene- ration. 10of the females (Ax) were kept on the semisynthetic control diet (Table 1) through- out the experimental period (about 130 days); 10 females (B x) received a semisynthetic iodine deficient diet during a period of 60 days, and 10 (C x) during a period of 133 days (Table 5). The adult males were used for mating only and they were mostly fed with the commercial mouse and rat diet (Table 1). The female progeny from the first pregnancy of Ax, and Cx, rats were considered as the second generation (A 2 and C 2 respectively) (Tables 3 & 5). The A 2 and C 2 females were mated at 70 days of age with the above mentioned 5 males and the pups born (third gene- ration) were killed at 25 days of age (Table 3). The male progeny from the first pregnancy (Experiment I) of the Ax and Cx rats were killed at 60 days ofage (Table 2). Bothfemale and male progeny from the second pregnancy ofAj and Cx females and those from the first pregnancy of the Bx females (Experiment II) were killed at 60 days ofage (Table 4). The descendants received the same diet as their dams with the exception of a group of pups born to B x dams in Experiment 11, which were transferred into the commercial mouse and rat diet directly after weaning at 30 days ofage (Table 4). The A1; B x and Cx dams were killed as soon as theirpups had been weaned in Experiment 11. The A 2 and C 2 dams were killed as soon as their pups were killed at 25 days ofage (Tables 3 & 5). The following indices were used to indicate female fertility a) number of dams concei- ving, b) pups dropped days after the start of the mating period, c) number and weight of the pups at birth, d) pup mortality during the suckling period, and e) total weight of the female sex organs. Lactational ability of the rats with pups was investigated by measuring the growth ofthe pups during the first 15 days after birth. Also the growth performance of the progeny from weaning (at 30 days) up to 60 days of age was investigated. Results and discussion Experiment I. The results obtained from Experiment I have been summarized in Tables 2 & 3. The values in Table 2 indicate that the A x rats conceived better, dropped 141 Table 4. Experiment 11. First generation and its progenyfrom the first gestation in group Bj and from the second gestation in groups Aj and Cj. Group No. of Pups born No. of Mean at 30 days post partum at 60 days post partum dams days after pups birth Survival Mean body No. of Body Thyroid Relative Weight of mating born weight % weight of pups weight weight thyroid the sex g g the pups g mg weight organs** 8 f control diet A, Control 10* 28.8 69 4.6 76.8 60.9 \ $ 30 200.1 8.14 4.08 2.227 1j?23 154.3 7.15 4.83 0.411 f commercial diet |